When performing an allocating work for a wire (liner body), a wire-tensioning apparatus equipped with wire grippers coupled at both ends of an extensible rod-shaped body is used to create looseness in a portion where an allocating work is performed by pulling the wire. The wire-tensioning apparatus grips the wire with the wire grippers on both sides, then shortens the interval between the wire grippers coupled to both ends of the rod-shaped body by decreasing the length of the rod-shaped body to thereby create looseness in the electric wire between both ends gripped by the wire grippers. The wire-allocating work can be easily performed by cutting desired portions in the loosened electric wire. A wire gripper disclosed in a patent document 1 is opened to the public as prior art of gripping such an electric wire.